High speed optical sub-assembly with ceramic carrier

ABSTRACT

A multilayer ceramic carrier for an optical element includes a terraced cavity for retaining a vertically receiving or vertically emitting optical element. The multilayer ceramic carrier includes conductive traces interposed between the ceramic layers and which extend into the terraced cavity along the trenches formed in the cavity. A vertical cavity surface emitting laser or vertically receiving optical element is wire bonded to the conductive traces which extend into the cavity. In one embodiment, the terraced cavity of the multilayer ceramic carrier includes a VCSEL and photodetector therein, the photodetector capable of monitoring the output optical power of the VCSEL. The method for forming the multilayer ceramic carrier includes forming a plurality of layers of ceramic tape, joining the layers, then co-firing the stacked layers. The multilayer ceramic carrier is joined to a plastic optical housing which includes an aperture for securing an optical fiber. The fiber launch direction is generally orthogonal to the optical surface of the vertically emitting or vertically receiving optical element secured within the ceramic carrier. The optical subassembly comprising the plastic optical housing and ceramic carrier is mounted on the surface of a printed circuit board or adjacent the edge of a printed circuit board, such that the light emitted or detected by the optical element, preferably travels along a fiber launch direction parallel to the surface of the printed circuit board. The optical assembly may be joined to the printed circuit board using various connectors capable of carrying an electrical signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority of provisional application Ser. No.60/237,341 filed on Sep. 29, 2000, entitled “High-Speed OpticalSubassembly with Ceramic Carrier”, and provisional application Ser. No.60/304,925 filed on Jul. 11, 2001, entitled “Edge Mount, Leaded CeramicOptical Subassembly”, the contents of each of which are hereinincorporated by reference.

FIELD OF THE INVENTION

The present invention is related, most generally, to the manufacture andpackaging of optical sub-assemblies (OSAs). More particularly, thepresent invention is related to packaging vertically-emitting opticaldevices such as vertical cavity surface emitting lasers (VCSELs), andvertically-receiving solid state optical devices such as photodetectors,within OSAs. The present invention also relates to the method andapparatus for mounting the OSA on a printed circuit board or othermounting surface.

BACKGROUND OF THE INVENTION

In today's rapidly-advancing optical electronics industry, verticalcavity surface emitting lasers have become preferred as the opticalsource. Vertical cavity surface emitting lasers—also referred to asVCSELs—are favored because of the ease of their manufacture, therepeatability of the manufacturing process used to form the VCSELs, thereduced substrate area each VCSEL requires, and because of the superioruniformity of the VCSELs formed within the same substrate. Furthermore,vertical cavity surface emitting lasers typically require less power todrive their lasing action than edge emitting lasers. A principalcharacteristic of a VCSEL is that it emits beams vertically, i.e. in adirection normal to the P-N junction and the surface of thesemi-conductor substrate on which it is fabricated. There are at leasttwo issues, however, associated with the use of VCSELs in optoelectronicsystems.

One issue is monitoring the optical output of the VCSEL. In conventionaledge emitting lasers, one end of the laser serves as the emitting edge,while the opposite end may be used to monitor optical power once therelative amount of light emitted out of the respective ends isdetermined. A small portion of light is typically emitted out of the endthat is not used as a primary optical source. Most commerciallyavailable VCSELs emit light normal to the surface in which they areformed. Therefore, in order to monitor optical power, this emitted beammust be monitored. It is challenging to do this without blocking orotherwise obstructing the optical beam, which must also be focused ontoan optical transmission medium. It is thus desirable to provide adetector that monitors the emitted optical beam without attenuating orcompromising it.

Another issue associated with the use of VCSELs is that the lightemitted from a VCSEL mounted on a module according to conventionaltechniques, is normal to the fiber launch direction used in most opticalcommunication applications. Fiber-connected optoelectronics inhigh-speed applications typically require that light is advantageouslyemitted and received parallel to the plane of the module such as thesurface of a printed circuit board. The launch direction of the opticalfiber, along which light travels, is also preferably parallel to theplane of the module. In this manner, the light is emitted and receivedalong a direction generally parallel to the path of the electric signal.It is therefore a challenge to mount a VCSEL within an opticalsubassembly mounted on a printed circuit board and which will be coupledto an optical fiber oriented generally parallel to the printed circuitboard. When using vertically-transmitting optical devices such asVCSELs, either the electrical or optical path must make a 90° turn inorder to achieve parallel connection with the fiber according toconventional packaging technologies. Mirrors may be used to bend thelight 90° to try to focus the emitted light onto the end face of a fiberwithout compromising the quality of the optical signal. Even if theVCSEL is mounted such that it is rotated 90° with respect to the printedcircuit board, the stability of the optical subassembly (OSA) mountedsideways on the board becomes a concern, and the nature and length ofthe electrical connections between the OSA and the board also becomes aconcern, especially in high-frequency applications where a constant andcontrolled impedance is typically required. Moreover, there are spaceconstraints in many applications that limit OSA designs, and thereforethe ability to mount a vertically-emitting optical device within an OSAand perpendicular to the module such that it emits light parallel to theplane of the module. Any such space constraints associated with mountingan OSA on a printed circuit board mandate that the OSA be of minimaldimension, which may make it difficult to utilize OSAs large enough toinclude additional components capable of turning the optical path.Similar shortcomings and challenges may be present for mountingvertically-receiving optical devices as well.

The cost of an OSA generally increases with the number of componentswhich combine to form the OSA. Such components typically include aseparately formed and assembled ball lens to focus the light emiffedfrom a laser into the end face of an optical fiber. It would thereforebe desirable to reduce cost by eliminating components such as the balllens.

What is needed to address the various shortcomings of the conventionaltechnology, is a method and apparatus for mounting a vertically-emittingor receiving optical element in an optical subassembly such that theoptical element is oriented to emit or receive light along a fiberlaunch direction that is parallel to the surface of the module on whichthe optical subassembly is mounted.

SUMMARY OF THE INVENTION

The present invention provides various embodiments of ceramic carriers,optical sub-assemblies, and assemblies in which the opticalsub-assemblies are mounted on a mounting surface, and methods forforming the ceramic carriers and optical sub-assemblies, as well asmethods and arrangements for mounting the optical sub-assemblies.

In one embodiment, the present invention provides an optical subassemblywhich includes a multilayer ceramic carrier. The ceramic carrier isformed of multiple ceramic layers. The multilayer ceramic carrierpreferably includes a terraced cavity. An optical element may be mountedwithin the cavity such that it emits light in a direction generallyorthogonal to the base surface of the terraced cavity. The terracedcavity preferably includes a terrace formed on at least one of theinterior sidewalls, and conductive traces formed on at least one of theceramic layers and which are interposed between the ceramic layers andinternal with respect to the ceramic carrier. The multilayer ceramiccarrier may form part of a TOSA (transmit optical subassembly) andinclude a VCSEL as the optical element.

According to another embodiment of the present invention, the multilayerceramic carrier may form part of a ROSA (receive optical subassembly)and include a photodetector and associated components therein.

Another embodiment of the present invention includes a method forforming a multilayer ceramic carrier. In the preferred embodiment, themethod includes providing a plurality of layers of ceramic tape, eachhaving an aperture, and at least two of the apertures having differentsizes. The method includes aligning the plurality of layers of ceramictape over one another such that the apertures are aligned over oneanother, and the stack of plurality of layers is aligned over a bottomceramic layer. The layers are preferably joined together, then co-firedat an elevated co-firing temperature to permanently join the ceramiclayers.

Another embodiment of the present invention is an optical carrier whichincludes an optical source disposed within a terraced cavity. Theterraced cavity includes conductive traces formed along at least one ofthe terraces of the terraced cavity. The optical source is wire-bondedto a conductive trace formed along the terrace. A photodetector isincluded within the terraced cavity and is capable of detecting lightemitted by the optical source and monitoring optical power.

According to another exemplary embodiment, the present inventionprovides an optical component including a ceramic carrier having abottom surface and an opposed top surface which is generally parallel tothe bottom surface, a cavity extending down from the top surface andincluding interior sidewalls, and a base surface. A VCSEL and aphotodetector are disposed on the base surface, the VCSEL capable ofemitting light substantially orthogonal to the base surface, and thephotodetector capable of monitoring light emitted by the VCSEL.

The present invention also preferably provides an optical subassemblyincluding the ceramic carrier coupled to an optical housing. The ceramiccarrier includes either a vertically-emitting or vertically-receivingoptical element therein, and the optical subassembly is configured to beconterminously mounted on a mounting surface such that the opticalelement either emits light generally parallel to the mounting surface orreceives light traveling generally parallel to the mounting surface. Theoptical housing includes an aperture for retaining an opticaltransmission medium within an optical ferrule such that the lightemitted from the VCSEL travels along the optical transmission medium.

According to another embodiment of the present invention, a method forforming an optical subassembly by joining a ceramic carrier to anoptical housing, is provided. The ceramic carrier includes a cavityextending from a first surface and includes a VCSEL disposed within thecavity such that the VCSEL emits light out of the cavity andperpendicular to the top surface. The method preferably includesproviding an optical housing having opposed sets of legs and acylindrical portion having an axis which is substantially parallel tothe legs and capable of retaining an optical transmission medium Themethod provides for covering the cavity with a glass member, thenplacing the legs on the top surface such that the legs of the opticalhousing straddle the glass, then aligning the optical housing to theceramic carrier such that the optical elements are aligned, and fixingthe optical housing into position with respect to the ceramic carrier byapplying a first epoxy. The first epoxy is cured using either UVradiation, visible light, or RF curing, then the optical housing issecured to the ceramic carrier by applying and curing a second epoxy,the second epoxy being either thermally curable, UV-curable, RF curable,or visible light-curable.

Another embodiment of the present invention is an assembly including anoptical subassembly mounted on a mounting surface of a board such that avertically emitting or vertically receiving optical element includedwith the optical subassembly, emits or receives light along a directiongenerally parallel to the mounting surface. The optical subassemblyincludes a ceramic carrier coupled to an optical housing. The opticalelement is included within the ceramic carrier and includes an opticalsurface perpendicular to the mounting surface. The ceramic carrierincludes an outer sidewall which is conterminously joined to themounting surface.

According to yet another embodiment of the present invention, anassembly is provided which includes an optical element secured within anoptical subassembly which is mounted adjacent an edge of a board such asa printed circuit board. The optical element may be avertically-emitting optical element or a vertically-receiving opticalelement which is capable of emitting or receiving light a directionsubstantially parallel to the board.

The present invention preferably also provides a method for joining anoptical subassembly to a printed circuit board such that the opticalsubassembly is mounted adjacent an edge of the printed circuit board,and a VCSEL included within the optical subassembly emits lightgenerally parallel to the surface of the printed circuit board. Themethod includes the steps of providing an optical subassembly includinga VCSEL oriented to emit light along a first direction, and a pluralityof conductive leads extending from the optical subassembly substantiallyparallel to the first direction, providing a printed circuit boardhaving an edge and including a plurality of conductive padscorresponding to the plurality of conductive leads extending to theedge, then joining the conductive leads of the optical subassembly tothe corresponding conductive pads of the printed circuit board.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is best understood from the following detaileddescription, when read in conjunction with the accompanying drawings. Itis emphasized that, according to common practice, the various featuresof the drawing are not to scale. On the contrary, the dimensions of thevarious features are arbitrarily expanded or reduced for clarity and toemphasize features of the present invention. Like numerals refer to likefeatures throughout the specification and drawing. Included in thedrawings are the following figures:

FIG. 1 is a cross-sectional view showing an exemplary embodiment of amultilayered ceramic carrier according to the present invention;

FIG. 2 is a plan view of conductive traces formed on a ceramic layer ofthe ceramic carrier such as shown in FIG. 1;

FIG. 3 is a plan view showing another exemplary ceramic layer whichincludes an exemplary aperture;

FIG. 4 is a plan view showing an exemplary arrangement of a VCSEL andtwo photodetectors within a ceramic carrier;

FIG. 5 is a plan view showing an exemplary arrangement of aphotodetector within a ceramic carrier;

FIG. 6 is a cross-sectional view showing an exemplary embodiment of aVCSEL and a photodetector within a ceramic carrier;

FIG. 7 is a cross-sectional view showing another exemplary embodiment ofa VCSEL and a photodetector within a ceramic carrier;

FIG. 8 is a cross-sectional view showing another exemplary embodimentincluding two VCSELs and a photodetector within a terraced cavity formedwithin a ceramic carrier;

FIG. 9 is a cross-sectional view of another exemplary embodiment showingtwo VCSELs and a photodetector formed within a terraced cavity formedwithin the ceramic carrier;

FIG. 10 is a cross-sectional view of another exemplary embodimentshowing a VCSEL and two photodetectors formed within a terraced cavityand coupled to an optical housing;

FIG. 10A is an expanded cross-sectional view showing a glass memberjoined to the ceramic carrier;

FIG. 11 is an expanded perspective view of the ceramic carrier, solderpre-form, and glass member of an exemplary optical subassembly prior tothe components being joined;

FIG. 12 is a perspective view of an exemplary embodiment of a ceramiccarrier according to the present invention;

FIG. 13 is a perspective view showing the ceramic carrier coupled to anexemplary optical housing to form an OSA according to the presentinvention;

FIG. 14 is a cross-sectional view of an exemplary optical housing;

FIG. 15 is a perspective view showing a base portion of an opticalhousing coupled to a ceramic carrier;

FIG. 16 is a cross-sectional view showing an exemplary arrangement forcoupling the base of the optical housing to the ceramic carrier;

FIG. 17 is a cross-sectional view showing an exemplary ceramic carrierincluding a recessed portion;

FIG. 18 is a perspective view of a ceramic carrier including a recessedtop surface;

FIG. 19 is a plan view of an exemplary bottom surface of an exemplaryceramic carrier;

FIG. 20 is a perspective view showing an exemplary arrangement formounting an OSA on a mounting surface;

FIG. 21 is a perspective view showing another exemplary arrangement formounting an OSA on a mounting surface;

FIG. 22 is a side view showing yet another exemplary arrangement formounting an OSA on a mounting surface;

FIG. 23 is a partial side view showing another exemplary arrangement formounting an OSA on a mounting surface;

FIG. 24 is a plan view showing an exemplary OSA mounted on a mountingsurface;

FIG. 25 is a perspective view of an exemplary OSA including a plastichousing, ceramic carrier, and mounting pins;

FIG. 26 is another perspective view of the exemplary optical subassemblyshown in FIG. 25;

FIG. 27 is a perspective view showing an exemplary method for couplingthe base of the optical housing to the ceramic carrier;

FIG. 28 is a perspective view showing an exemplary OSA mounted to theedge of a printed circuit board;

FIG. 29 is a plan view of an exemplary printed circuit board accordingto the present invention;

FIG. 30 is a perspective view showing exemplary relief features formounting the ceramic carrier on a mounting surface using relieffeatures; and

FIG. 31 is a cross-sectional view showing an exemplary OSA including aceramic carrier coupled to a fiber receptacle by means of a bridge.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides various embodiments of ceramic carriers,optical sub-assemblies, and assemblies in which the opticalsub-assemblies are mounted on a mounting surface, and methods forforming the ceramic carriers and optical sub-assemblies, as well asmethods and arrangements for mounting the optical sub-assemblies. Thepresent invention covers both transmit optical sub-assemblies (TOSAS)and receive optical sub-assemblies (ROSAs). The various aspects of thepresent invention are preferably utilized in conjunction with verticallyemitting devices such as VCSELs. Vertically emitting devices emit lightout of the surface of the substrate in which they are formed. Thepresent invention also may be used with vertically receiving devicesthat receive and detect light preferably directed vertically towards thesurface of the substrate in which they are formed.

FIG. 1 is a cross-sectional view showing exemplary multilayer ceramiccarrier 10. In the exemplary embodiment shown, ceramic carrier 10 isgenerally box-shaped and includes five layers, but any number of layersmay be used according to other exemplary embodiments. In the exemplaryembodiment shown in FIG. 1, ceramic carrier 10 includes bottom layer 19,top layer 26, and intermediate layers 20, 22 and 24. The layers areindividually formed to have different-sized apertures, and the aperturesare aligned over one another such that the formed ceramic carrier 10includes terraced cavity 6. Terraced cavity 6 includes sidewalls 14 andterraces 16. Terraced cavity 16 may be formed centrally in ceramiccarrier 10 or it may be off-center. Terraces 16 result when anunderlying ceramic layer includes a section which extends into terracedcavity 6 to a greater extent than the overlying layer. In an exemplaryembodiment, a conductive trace 38 extends along terrace 16. In theexemplary embodiment shown, ceramic carrier 10 includes top surface 12,bottom surface 8, and external sidewalls 9. In the exemplary embodimentshown, each of top surface 12 and opposed bottom surface 8 aresubstantially planar and parallel to one another. Terraced cavity 6includes base surface 18, and VCSEL 2 and a photodetector 4 are disposedon base surface 17. VCSEL 2 is coupled to conductive trace 38 by meansof wire bond 18. The thicknesses of each ceramic layers 19, 20, 22, 24and 26 may range from 100 to 1500 microns. Other thicknesses may be usedaccording to other exemplary embodiments.

Each of ceramic layers 19, 20, 22, 24 and 26 are preferably formed ofco-fired ceramic tape. According to the various exemplary embodiments, ahigh-temperature co-fired ceramic tape (HTCC) or low-temperatureco-fired ceramic (LTCC) material may be used as the ceramic tape.According to an exemplary embodiment, DuPont 951 Green Tape™ may beused. According to other exemplary embodiments, materials such as DuPont943 Green Tape™ or Ferro A6M ceramic tape may be used. The ceramic tapesare typically formed of alumina, aluminum nitrate or other similarmaterials, but other suitable materials may be used alternatively.According to an exemplary embodiment, multiple sheets of ceramic tapeare aligned over one another and permanently joined together to form anarray of individual ceramic carriers (10) that are subsequentlyseparated.

Traces of conductive material may be formed on the individual ceramiclayers prior to assembly, using conventional methods and conventionalconductive materials. In an exemplary embodiment in whichlow-temperature co-fired ceramic is used, metals such as silver (Ag) andgold (Au) may be used as the conductive material. In HTCC applications,tungsten, W or tungsten-molybdenum WMo may be used due to their highermelting temperatures. In high-frequency applications, materials of thehighest conductivity such as silver and gold are preferred, andtherefore an LTCC process is typically used in high-speed applications.Any or all of the individual ceramic layers of the array may includevias 32 that extend through the ceramic layer and electrically coupleconductive traces formed on the layers. According to the exemplaryembodiment in which conductive traces are formed on the individualceramic layers prior to assembly, the assembled multilayer ceramiccarrier 10 therefore includes conductive traces formed integrallytherein and disposed between adjacent ceramic layers such as betweenlayer 22 and layer 24. In an exemplary embodiment, a portion of one ormore conductive traces preferably extends into terraced cavity 6 alongat least one terrace 16 formed within terraced cavity 6. The conductivetrace thereby terminates within terraced cavity 6 and is electricallycoupled by way of wire bonding or other means, to a VCSEL,photodetector, or other optical component formed within terraced cavity6. Conductive traces may additionally or alternatively be formed alongbase surface 17. In an alternative embodiment, either of VCSEL 2,photodetector 4, or various other electrical components included withincavity 6, may be coupled to the conductive traces formed on base surface17.

The method for forming ceramic carrier 10 includes aligning sheets ofthe ceramic tape which form the component layers, such as layers 19, 20,22, 24 and 26, over one another, then permanently joining the layers. Inan exemplary embodiment, all but the lower of the ceramic layers willinclude an aperture therethrough. The apertures may be of different sizeand are aligned over one another to form terraced cavity 6. Terracessuch as terrace 16 may be formed along any or all of internal sidewalls14. Terraces 16 may extend partially or completely along respectivesidewalls 14. In an exemplary embodiment, terraces which are formed onopposite internal sidewalls 14 may be at the same level within terracedcavity 6, or they may be formed at different levels such as shown inexemplary FIG. 1. After the individual layers of ceramic tape arealigned over one another, the sheets may be joined using a nominaltemperature of about 80° C., but other temperatures may be usedalternatively. After the sheets are joined together, the ceramiccarriers are co-fired in a furnace according to conventional methods.For HTTC materials, co-firing temperatures on the order of 1600° may beused, and for LTCC materials, an exemplary co-firing of about 800° maybe used. The preceding temperatures are intended to be exemplary only,and other temperatures may be used in each case, According to theembodiment in which sheets of ceramic tape are joined together to forman array of ceramic carriers 10, the individual ceramic carriers 10 maybe separated into individual ceramic carriers, either prior to or afterthe co-firing operation. Conventional processes may be used to separatethe individual ceramic carriers 10.

FIG. 2 is a plan view showing exemplary layer 20 of ceramic carrier 10.FIG. 2 shows exemplary conductive traces 30 and conductive vias 32,which extend through ceramic layer 20 and couple conductive traces 30 tocorresponding conductive traces formed on a layer or layers beneathceramic layer 20 such as conductive traces that may be formed on ceramiclayer 19, shown in FIG. 1. When the layers are joined together to forman integral ceramic carrier 10 such as shown in FIG. 1, conductivetraces 30 are integral to the ceramic carrier and interposed between theindividual layers and coupled to other conductive traces formed on otherintegral layers by way of the conductive vias. Ceramic layer 20 alsoincludes aperture 36 which defines and forms part of terraced cavity 6in the integral unit. In the exemplary embodiment shown in FIG. 1, layer20 is the wire-bonding shelf which includes a portion 38 of conductivetrace 30 which extends into terraced cavity 6 such as shown in FIG. 1.The portion of ceramic layer 20 which forms terrace 16 in ceramiccarrier 10 is shown by the dashed line in FIG. 2.

FIG. 3 is a plan view showing an exemplary ceramic layer such as ceramiclayer 24 of multilayer ceramic carrier 10 shown in FIG. 1. Ceramic layer24 includes cut-out or aperture 40 which extends through ceramic layer22. The aperture, as well as aperture 36 of ceramic layer 20 such asshown in FIG. 2, may be formed using a conventional punching operationwhich punches a hole through the ceramic layers when they are in tapeform, but other techniques may be used alternatively. The apertures maybe formed in many of the ceramic layers, and may be of differentdimension and configuration. The cut-outs or apertures are aligned overone another in the multilayer ceramic carrier 10. Corners 41 of ceramiclayer 24 which extend into aperture 40 may be aligned over a similarstructure in the subjacent layers and may therefore form terraces 16 ifthe opening formed in a superjacent layer or layers, is larger thanaperture 40. For example, if the aperture formed in a superjacent layersuch as layer 26 shown in FIG. 1, is bounded by dashed line 43, thencorners 41 will form terraces 16.

Returning to FIG. 1, it can be seen that the opposed terraces 16 shownas formed along opposed sidewalls 14 of terraced cavity 6 are formedfrom different ceramic layers and are therefore of different heightswithin terraced cavity 6. Stated alternatively, the opposed terraces areformed on stacks comprised of different numbers of ceramic layers. Thedimensions of terraced cavity 6, the shape of the cavity, and thevertical and horizontal dimensions of the ceramic carrier will vary byapplication, and therefore, any suitable set of dimensions may be used.Terraces may be formed along the entirety or portions of either or allof the interior sidewalls such as sidewalls 14A, 14B, 14C and 14D shownin FIG. 2.

FIG. 4 is a top view showing terraced cavity 6 of ceramic carrier 10.Terraced cavity 6 includes two terraces 16 formed on opposed sidewalls14. Base surface 17 of terraced cavity 6 is substantially parallel totop surface 12 in the exemplary embodiment. Exemplary VCSEL 2 andexemplary photodetectors 4 are disposed on base surface 17. In theexemplary embodiment, photodetectors 4 are formed on opposed sides ofVCSEL 2, but other arrangements may be used according to other exemplaryembodiments. Each of VCSEL 2 and photodetectors 4 include a wire bond 18coupling the component to portion 38 of conductive traces formed onterrace 16. In another exemplary embodiment, VCSEL 2 and photodetectors4 may be wire bonded to conductive traces formed on base surface 17 (notshown). VCSEL 2 may be a top side emitting VCSEL or a bottom sideemitting VCSEL. By top side emitting VCSEL, it is meant that the VCSELemits light out of an emitting surface formed on the substrate surfaceon which the VCSEL is formed. In an exemplary embodiment, VCSEL 2 andphotodetector 4 may be integrally formed on the same substrate such asdescribed in U.S. application Ser. No. 09/348,353, entitledCLOSELY-SPACED VCSEL AND PHOTODETECTOR FOR APPLICATIONS REQUIRING THEIRINDEPENDENT OPERATION, filed Jul. 7, 1999, the contents of which areherein incorporated by reference.

Various other additional and alternative components may be includedwithin terraced cavity 6, and arranged in various other configurations,according to other alternative embodiments. Terraced cavity 6, forexample, may be formed large enough to include additional semiconductorand electronic components besides the primary optoelectronic device.Additional components that may be included in terraced cavity 6 ofceramic carrier 10 are resistors, monitor diodes, capacitors, inductors,and laser drivers in the exemplary embodiment in which the OSA is atransmit optical subassembly (TOSA). According to the exemplaryembodiment in which the optical subassembly is a ROSA (receive opticalsubassembly), transimpedance amplifiers, transimpedance limitingamplifiers, resistors, capacitors, inductors, and high speed detectorsmay be among the components additionally included within the OSA. Eachof these components may be wire bonded to conductive traces which extendinto terraced cavity 6. The photodetectors discussed in the presentapplication, such as photodetector 4, may be photodiodes or othersuitable vertically receiving monitor photodetectors or monitor diodesused in the optoelectronics industry. In an exemplary embodiment,photodetector 4 may be a p-i-n photodetector. The exemplary p-i-nphotodetector may be configured to detect light from the top side or thebottom side. For brevity, the singular term “photodetector”will be usedhereinafter, to describe all such photodetector devices. The VCSELs,photodetectors and other components may be joined to base surface 17using conventional mounting techniques. They may, for example, beflip-chip mounted, preferably when a bottom emitting VCSEL, or bottomdetecting photodetector is used.

FIG. 5 is a plan view showing another exemplary ceramic carrier 10including terraced cavity 6. Terraced cavity 6 includes base surface 17which is parallel to top surface 12 and also parallel to bottom surface8. Photodetector4 is mounted on base surface 17 and electrically coupledby means of wire bond 18 to portion 38 of a conductive trace. Accordingto an exemplary embodiment, this ROSA arrangement will advantageouslyinclude additional devices, such as a transimpedance amplifier ortransimpedance limiting amplifier (not shown) disposed on base surface17 along with photodetector 4 to aid in processing the optical signalreceived by photodetector 4, and converting the optical signal to anelectrical signal. According to other exemplary embodiments in which theoptical subassembly is a ROSA, other additional components, as above,may be included within the OSA.

In each of the exemplary embodiments shown in FIGS. 4 and 5, theconductive traces that include portion 38, which extends into terracedcavity 6, further extend integrally within ceramic carrier 10 andpreferably between the stacked ceramic layers which combine to formceramic carrier 10.

FIG. 6 is a cross-sectional view showing an exemplary arrangement ofcomponents within exemplary terraced cavity 6 of ceramic carrier 10. Inthis exemplary embodiment, multiple terraces 16 are formed at variousheights. FIG. 6 shows VCSEL 2 and photodiode 4 each formed on basesurface 17. Each of VCSEL 2 and photodetector 4 are wire-bonded toconductive traces and to further electrical components (not shown) bymeans of wire bond 18. The wire bonding may be carried out usingconventional means. VCSEL 2 and photodetector 4 are arranged adjacentone another on base surface 17. In this manner, the emitting surface ofthe VCSEL and absorbing surface 56 of photodetector 4 are preferablyparallel to each other and the base surface as well as the top surface12 and the bottom surface (not shown) of ceramic carrier 10.

Reflective/transmissive member 44 preferably rests on opposed terraces16A and 16B which are shown to be different heights.Reflective/transmissive member 44 is therefore acutely angled withrespect to base surface 17 and not parallel to base surface 17. VCSEL 2preferably emits light along direction 52 which is substantiallyorthogonal to base surface 17, top surface 12, and the bottom surface(not shown) of the ceramic carrier 10. Reflective/transmissive member 44forms tilt angle 46 with respect to direction 52 of light emitted byVCSEL 2. Reflective/transmissive member 44 is chosen so that a majorityof light emitted by VCSEL 2 is preferably transmitted through the memberand may be focused onto an optical fiber or other optical transmissionmedium (not shown) disposed above optical lens 50. Exemplary opticallens 50 will be discussed below in conjunction with the optical housingjoined to ceramic carrier 10 to form an optical subassembly (OSA). In anexemplary embodiment, 8-9% of the light emitted by VCSEL 2 is reflectedby the reflective/transmissive member 44 but other percentages may beachieved according to other embodiments.

Reflective/transmissive member 44 may be formed of glass according toone exemplary embodiment, but other materials may be used according toother exemplary embodiments. The glass may be formed of standardborosilicate materials, such as BK7. The glass or otherreflective/transmissive member 44 may further be coated with a thincoating of reflective material such as aluminum fluoride or magnesiumfluoride to vary the reflectivity of reflective/transmissive member 44.Tilt angle 46 is chosen such that reflected portion 54 of light emittedby VGSEL 2 and reflected by reflective/transmissive member 44 ispreferably directed onto absorbing surface 56 of photodetector 4 so thatphotodetector 4 can be used to monitor the optical output power of VCSEL2. Reflective/transmissive member 44 is preferably chosen to reflect aknown percentage of emitted light. According to other exemplaryembodiments, the percentage of emitted light which is reflected byreflective/transmissive member 44 and detected by photodetector 4, maybe determined experimentally using various techniques. In this manner,then, the amount of light detected by photodetector 4 corresponds to aknown total amount of light emitted by VCSEL 2. Alternatively stated,the amount of light sensed by photodetector 4 can be correlated to anoptical output power of VCSEL 2. It can be understood that opposedterraces 16A and 16B can be configured to determine tilt angle 46, whichmay be varied and that the photodetector may be placed in variouspositions to accept a suitable amount of reflected light. In anexemplary embodiment, reflective/transmissive member 44 may be joined toceramic carrier 10 to produce a hermetic seal beneathreflective/transmissive member 44.

The exemplary arrangement shown in FIG. 6 also includes secondreflective/transmissive member 48. Second reflective/transmissive member48 is joined to top surface 12 of ceramic carrier 10 and covers terracedcavity 6. In an exemplary embodiment, second reflective/transmissivemember 48 may be joined to top surface 12 such that it hermeticallyseals terraced cavity 6 of ceramic carrier 10. Secondreflective/transmissive member 48 may be formed of glass in an exemplaryembodiment and may be coated as described in conjunction withreflective/transmissive member 44. Other materials may be used to formsecond reflective/transmissive member 48 according to other exemplaryembodiments. Hereinafter, second reflective/transmissive member 48 willbe simply referred to as glass cover 48, but it should be understoodthat alternative materials may be used. Glass cover 48 may be arrangedto reflect a known or determined portion of light emitted by VCSEL 2,such that it may be detected by photodetector 4. As will be shown below,photodetector 4 may be configured to sense light which is emitted byVCSEL 2 and reflected off of either or both of glass cover 48 andoptical lens 50. Optical lens 50 is part of an optical housing joined toceramic carrier, as will be described below.

Photodetector 4 can therefore be used to monitor the optical output ofVCSEL 2. Various conventional methods, feedback loops, and analyticalmeans may be used in conjunction with various electrical circuits toadjust the optical power of VCSEL 2 based on the amount of lightdetected by photodetector 4. Photodetector 4 may be formed usingconventional methods and will preferably be formed of a material whichhas good absorption characteristics at the wavelength of light beingused. In an exemplary embodiment, silicon may be used as photodetector4, and used for detecting 850 nm light emitted by VCSEL 2. According toother exemplary embodiments, VCSEL 2 may emit light at any of variousother wavelengths ranging up to 1650 nm. Photodetector 4 is chosen forcompatibility with the wavelength of light emitted by VCSEL 2.

The dimensions of terraced cavity 6 are chosen and components such asVCSEL 2 and photodetector 4 are positioned so that the length of wirebond 18 is minimal. This is especially desirable for high frequencyapplications in which a controlled and constant impedance is essentialat the operating frequency used. It should be understood that theconfiguration of components with terraced cavity 6 and the shape ofterraced cavity 6 as shown in FIG. 6 is exemplary only and various otherarrangements of components, configurations of terraced cavity 6 andmeans for hermetically sealing terraced cavity 6 may be used accordingto other exemplary embodiments.

According to other exemplary embodiments, ceramic carrier 10 may beformed of materials other than layers of ceramic tape. According to yetanother exemplary embodiment, a carrier shaped and configured such asceramic carrier 10 may be formed to include a terraced cavity andconductive traces formed along the terraces and which are electricallycoupled to optical components within terraced cavity, may be formed ofother materials. In an exemplary embodiment, the carrier may be formedof multiple layers of printed circuit board material or other suitabledielectric or polymeric materials. The ceramic carrier may be formed ofmaterials such as FR4, Duroid, Isoclad, Arlon, or other suitableconventional materials. The carrier may be formed by machining or it maybe formed by stacking a plurality of discrete layers over one anothersuch as described in conjunction with the discrete layers of ceramictape used to form multilayer ceramic carrier 10, as shown and describedherein.

FIG. 7 shows another exemplary arrangement of components within terracedcavity 6 of ceramic carrier 10. The arrangement shown in FIG. 7 issubstantially similar to the arrangement shown in FIG. 6, except theangled, reflective/transmissive member shown in FIG. 6, is not present.Additionally, glass cover 48 is formed within recessed portion 180 whichis recessed below top surface 12 of ceramic carrier 10. Morespecifically, glass cover 48 is joined to recessed surface 181 ofrecessed portion 180. In the exemplary embodiment shown in FIG. 7,photodetector 4 may be configured to detect light emitted by VCSEL 2 andreflected by optical lens 50, glass cover 48, or both of optical lens 50and glass cover 48. Optical lens 50 is formed of an optical housingjoined to ceramic carrier 10. Optical lens 50 is formed and configuredto direct light emitted by VCSEL 2 onto an optical transmission mediumsuch as an optical fiber (not shown). Optical lens 50 may be coated witha reflective material to reflect part of the light emitted by VCSEL 2,onto absorbing surface 56 of photodetector 4.

FIGS. 8 and 9 are each cross-sectional views showing additionalexemplary embodiments of arrangements of optical components withinterraced cavity 6, according to the present invention. In FIG. 8, twoVCSELs, VCSEL 2 and VCSEL 60 are shown and situated adjacent to oneanother. VCSELs 2 and 60 are preferably chosen to have virtually thesame optical performance characteristics. According to one exemplaryembodiment, the two VCSELs, 2 and 60 may be formed from the samesubstrate. VCSELs 2 and 60 are chosen such that when identicalelectrical power is applied to each of the VCSELs, the optical output ofone is substantially the same as the optical output of the other. It canbe seen that each of the two VCSELs, 2 and 60, are wire bonded by meansof wire bond 18 to respective terraces 16. The terraces to which theVCSELs are wire bonded include conductive traces thereon forelectrically coupling each of the VCSELs to other electrical components.Short wire bonds are preferably used. In FIG. 8, photodetector 62 ispositioned over VCSEL 60. Photodetector 62 may be joined to terrace 16,which may extend across terraced cavity 6, as indicated by dashed line63, in the exemplary embodiment shown. Conventional means may be used toposition and secure photodetector 62 over VCSEL 60. According to thisexemplary embodiment, VCSEL 2 is the data laser which emits the opticalsignal that is preferably coupled to an optical transmission medium. Thelight emitted from VCSEL 60 is directed at photodetector 62 which may bea photodiode according to the exemplary embodiment. In an exemplaryembodiment, VCSELs 2 and 60 are driven in parallel by common circuitry.Since it is known that VCSEL 2 and VCSEL 60 have substantially the sameelectrical and optical properties, the optical power sensed byphotodetector 62 which senses light emitted from VCSEL 60, is identical,or at least representative of, light emitted by VCSEL 2 and thereforethe optical signal. In this manner, light detected by photodetector 62may preferably be used to adjust the optical power of VCSEL 2 whichsupplies the optical signal to the optical transmission medium. Variousmethods and electrical circuits may be used for this feedback loop.

Referring to FIG. 9, photodetector 66 may alternatively be mounteddirectly on VCSEL 60 using conventional methods such as solder bumps andflip-chip mounting techniques. According to yet another exemplaryembodiment, a clear epoxy may be used to join photodetector 66 to VCSEL60. According to the exemplary embodiments shown in FIGS. 8 and 9, thepresent invention enables the monitor photodetector to captureessentially all of the light emitted from VCSEL 60. This enablesmonitoring of the AC power which may be used to provide a constantextinction ratio. It should also be understood that in the embodiment inwhich the photodetector is mounted directly on the VCSEL, the cavity mayalternatively be formed having straight sidewalls, and without terraces,or may otherwise be configured to house the second VCSEL and monitoringphotodiode.

FIG. 10 is a cross-sectional view showing another exemplary arrangementof components within terraced cavity 6 of ceramic carrier 10. FIG. 10shows VCSEL 2, photodetector 4, and further photodetector 70 formed onbase surface 17 of terraced cavity 6. Each of photodetector 4 andfurther photodetector 70 include absorbing surfaces 56 which aregenerally parallel to emitting surface 57 of VCSEL 2. Photodetector 4 iswire bonded to terrace 1 6L, further photodetector 70 is wire bonded toterrace 16R, and photodetector 7 is wire bonded to a terrace 16B whichmay be formed to the rear of the cross-sectional view shown in FIG. 10,and is indicated by dashed line 16B. Optical housing 75 includes opticallens 50 and is mechanically coupled to multilayer ceramic carrier 10.Bal lens 50 may be spherical or aspherical and includes surface 84 whichfaces VCSEL 2 and surface 85 opposite surface 84. According to variousexemplary embodiments, either or both of surface 84 and surface 85, maybe coated with various materials to enhance or reduce the reflection ofthe light emitted by VCSEL 2 while also focusing emitted light 81 onto afurther component such as an optical transmission medium (not shown) andreducing optical coupling of light back into VCSEL 2. According toanother exemplary embodiment, ball lens 50 may be formed of multiplecomponents such that an interface surface is formed between surfaces 84and 85 of ball lens 50.

According to the exemplary embodiment shown, VCSEL 2 emits emitted light81 in a direction generally orthogonal to emitting surface 57 of VCSEL2, base surface 17, and top surface 12. A portion of emitted light 81 ispreferably refracted within glass cover 48 and reflected from the topsurface of glass cover 48 as reflected light 80. Reflected light 80 isdirected towards absorbing surface 50 of further VCSEL 70. According toanother exemplary embodiment, a portion of emitted light 81 may bereflected from the lower surface of glass cover 48 and reflected towardsfurther photodetector 70. Glass cover 48 is chosen such that a majorityof emitted light 81 is preferably transmitted through glass cover 48. Ananti-reflective coating may be formed on either or both of top surface90 and interior surface 78 of glass cover 48. As an alternative to, orin addition to, light reflected from glass cover 48, a portion ofemitted light 81 may be reflected from surface 84 of ball lens 50 anddirected as reflected light 82 which is directed towards photodetector4. According to one exemplary embodiment, two photodetectors may be usedand disposed adjacent opposite sides of VCSEL 2. In one exemplaryembodiment, only light reflected by glass cover 48 may be directed toand absorbed by the photodetectors. According to another exemplaryembodiment, only light reflected by surface 84 of ball lens 50 may bedirected towards and detected by each of photodetector 4 and furtherphotodetector 70. According to one exemplary embodiment, ball lens 50may be formed integrally with optical housing 75. Ball lens 50 may beformed of a plastic chosen to be transmissive to the wavelength of lightemitted by VCSEL 2. According to another exemplary embodiment, ball lens50 may be formed separately and positioned within optical housing 75.Ball lens 50 may be formed of quartz, glass, or other materialsconventionally used as lens materials.

According to each of the exemplary arrangements of optical componentsshown in the preceding figures, other components may additionally oralternatively be formed within terraced cavity 6 of ceramic carrier 10.According to an exemplary embodiment, an integrated circuit or othersemiconductor devices listed above, may additionally or alternatively beincluded within terraced cavity 6.

Still referring to FIG. 10, glass cover 48 is joined to top surface 12of ceramic carrier 10. According to another exemplary embodiment, glasscover 48 may be joined to a recessed portion which is recessed below topsurface 12. Glass cover 48 is joined to ceramic carrier 10 usingexemplary features shown in FIG. 10A.

FIG. 10A is an expanded view showing a portion of FIG. 10, and showingglass cover 48 joined to top surface 12 of ceramic carrier 10. Accordingto the embodiment shown in FIG. 10A, the seal formed between ceramiccarrier 10 and glass cover 48, is a hermetic seal. The hermetic seal isprovided by ring 72 formed on surface 12, solder pre-form 74, and sealring 76 formed on internal surface 78 of glass cover 48. The componentsare joined using a method described in conjunction with FIG. 11.

FIG. 11 shows ceramic carrier 10 including cavity 73 extending downwardfrom top surface 12. Cavity 73 may be formed centrally on top surface12, or it may be off-center. Cavity 73 may be the terraced cavity shownand described above, or it may be a non-terraced cavity. Glass cover 48includes internal surface 78 which faces, and will be joined to, topsurface 12. Glass cover 48 also includes top surface 90. Ananti-reflective coating may be formed on either or both of top surface90 and interior surface 78 as described previously. Glass cover 48includes seal ring 76 preferably attached to interior surface 78 with aglass frit. Seal ring 76 is used to solder glass cover 48 to acorresponding ring 72 formed on ceramic carrier 10. Ceramic carrier 10includes ring 72 formed on top surface 12. Ring 72 may be formed ofmetal or kovar and may be a conductive trace formed of conventionalconductive materials. Seal ring 76 may also be formed of conventionalconductive material such as “Alloy 52.” Solder pre-form 74 is preferablypositioned between ceramic carrier 10 and glass cover 48. Ring 72,solder pre-form 74 and seal ring 76 are preferably substantially thesame size and shape or at least include a common boundary, and arealigned to one another; then the components are preferably joined to oneanother by soldering. In an exemplary embodiment, solder pre-form 74 maybe pre-attached to seal ring 76 of glass cover 48. After the componentsshown in FIG. 11 are joined together by soldering and cavity 73 isthereby sealed, ceramic carrier 10 is ready to be joined to an opticalhousing. According to other exemplary embodiments, other techniques maybe used to join glass cover 48 to top surface 12.

FIG. 12 is a perspective view showing terraced cavity 6 formed withinceramic carrier 10. Terraced cavity 6 includes internal sidewalls 14 Inthe northeast corner of terraced cavity 6, support member 93 is includedand includes terrace 16NE as a top surface. It should be understood thatin the southeast corner of terraced cavity 6, a similar support memberis included although not visible in the perspective view shown in FIG.12. It can be seen that support member 93 and terrace 16NE do not extendalong the entirety of any of sidewalls 14 which define terraced cavity6. Reflective/transmissive member 44 rests partially on terrace 16NE,and is therefore angled with respect to top surface 12 and the basesurface of terraced cavity 6 (not visible).

FIG. 13 is a perspective view showing multilayer ceramic carrier 10joined to optical housing 75 to form optical subassembly 130. Theconfiguration of optical housing 75 shown in FIG. 13 is intended to beexemplary only. Other configurations may be used alternatively. Opticalhousing 75 includes base portion 125 and barrel or cylindrical portion127 which includes aperture 129. Aperture 129 extends axially throughbarrel section 127 and essentially forms a hollow core of barrel section127.

In an exemplary embodiment, optical housing 75 may be formed of plastic.Plastics such as Ultem 1010, Ultem 1000, Topas 5013 or Topas 5713 may beused, but other conventional plastic materials may be used according toother exemplary embodiments. Aperture 129 formed within barrel portion127 is preferably configured to receive an optical ferrule including anoptical fiber or other optical transmission medium. The OSA 130 shown inFIG. 13 may be a TOSA (transmissive optical subassembly) or ROSA(receive optical subassembly). According to either exemplary embodiment,light propagated along an optical transmission medium retained axiallywithin aperture 129 of barrel portion 127 is received by or emitted froman optical component disposed within multilayer ceramic carrier 10.Multilayer ceramic carrier 10 is as described above and includes acavity such as the terraced cavity including optical components asdescribed above. Optical housing 75 shown in FIG. 13, is exemplary only,and various configurations other than the cylindrical/barrelconfiguration shown, may be used to retain an optical transmissionmember to propagate light emitted by or directed to an optical elementretained within ceramic carrier 10.

Optical housing 75 includes a ball lens therein and the ball lens may beformed as an integral portion of optical housing 75. The lens is used tofocus light from an optical transmission medium onto a light receivingdevice or to focus light emitted from a VCSEL onto an opticaltransmission medium. As such, according to the exemplary embodiment inwhich optical housing 75 is formed of plastic and includes an integrallens, the plastic is chosen for maximum transmissivity at the wavelengthof interest. According to other exemplary embodiments, optical housing75 may be formed of other suitable materials such as suitable metals orglass. Also according to other exemplary embodiments, optical housing 75may include the ball lens separately formed and secured within opticalhousing 75. In an exemplary embodiment, the separately formed ball lensmay be formed of glass or other suitable lens materials. According toyet another exemplary embodiment, the optical housing may include theball lens and barrel portion integrally formed of a plastic with thebase portion formed of another material. This exemplary embodiment willbe shown in FIG. 31. In the following figures, however, base portion andbarrel portion of optical housing 75 will be shown as an integrallyformed unit and referred to, collectively, as optical housing 75.

FIG. 14 is a schematic showing a cross-sectional view of optical housing75. In FIG. 14, optical housing 75 includes integral ball lens 50, baseportion 125, barrel portion 127, and aperture 129 which forms a hollowcore of barrel section 127. Other configurations may be used accordingto other exemplary embodiments. According to other exemplaryembodiments, base portion 125 may consist of a plurality of legs.

Optical housing 75 will preferably be joined to ceramic carrier 10 usingepoxy, soldering, or a combination of the two. According to oneexemplary embodiment, portions of optical housing 75 that are to bejoined to ceramic carrier 10, may be metallized, then a material such asa dielectric or polymeric material preferably chosen to reduce thecoefficient of thermal expansion (CTE) mismatch between optical housing75 and ceramic carrier 10 may be introduced between ceramic carrier 10and the metallized portion of optical housing 75.

Further methods and techniques for joining optical housing 75 to ceramiccarrier 10 are described below. In each case, the method for permanentlyjoining optical housing 75 to ceramic carrier 10 preferably includes thesteps of positioning the components with respect to one another, andaligning the optical transmission medium secured within optical housing75, to the optical source or optical detector contained within ceramiccarrier 10, then permanently joining the components.

FIG. 15 is a perspective view which shows base portion 125 (of theoptical housing) being joined to top surface 12 of ceramic carrier 10.Base portion 125 includes ledge 160 including top surface 162. Ledge 160extends peripherally around base section 125. According to otherexemplary embodiments, ledge 160 may only extend partially around basesection 125. For example, ledge 160 may appear only on opposed sides ofbase 125. Ledge 160 is preferably molded as an integral part of opticalhousing 75. In an exemplary embodiment, optical housing 75 includingledge 160 may be formed of plastic and by injection molding means. Ledge160 extends along the bottom of base section 125 and is directly joinedto top surface 12 as will be shown in FIG. 16.

FIG. 16 is a cross-sectional view showing optical housing 75mechanically coupled to top surface 12 of ceramic carrier 10 accordingto an exemplary embodiment. According to this exemplary embodiment,optical housing 75 may be formed of plastic. FIG. 16 shows two exemplarymeans for joining optical housing 75 to ceramic carrier 10—theperipheral ledge 160 shown and described in FIG. 15, and the pin170/receptacle 172 feature. Fillet 164 of epoxy is used to coupleoptical housing 75 to surface 12 of ceramic carrier 10. In an exemplaryembodiment, a UV-curable epoxy is used. According to other exemplaryembodiments, visible light-curable, RF curable or thermally curableepoxies may be used. Fillet 164 of epoxy is preferably bonded to surface12 of ceramic carrier 10, vertical surface 161, and extends overtopsurface 162 of ledge 160. Fillet 164 forms a stronger bond with surface12 than with vertical surface 161 of optical housing 75 formed ofplastic, for example. This is due to the slightly porous nature of theceramic carrier. Therefore, since the epoxy fillet 164 is bondedrelatively securely to surface 12, and since the epoxy itself formsinternally strong bonds, the portion of epoxy fillet 164 which liesabove surface 162 of ledge 160 acts as a clamp to hold plastic opticalhousing 75 into place. This embodiment provides the advantage that theadhesive shear strength between epoxy fillet 164 and vertical surface161 of optical housing 75 formed of plastic, is no longer the weak pointin the bonding between the two components. Rather, because of theclamping nature of epoxy fillet 164, the shear strength of the epoxymaterial itself is preferably substituted as the weak point in the bond.The shear strength of the epoxy itself is advantageously greater thanthe adhesive shear strength between the epoxy material and verticalsurface 161 of base portion 125 of optical housing 75. Therefore, thestrength of the bond between the two components is preferably increased.In an exemplary embodiment, width 166 of ledge 160 may be on the orderof 0.254 mm, but other widths may be used alternatively. As will beshown below, this embodiment finds particular advantage in the variousembodiments wherein OSA 130 is formed of the combination of ceramiccarrier 10 and plastic optical housing 75 and is to be mounted on itsside, with barrel section 127 of optical housing 75 ultimately extendinghorizontally and suspended over the mounting surface.

According to another exemplary embodiment, pins 170 may be formed toextend from surface 12 of ceramic carrier 10. Pins 170 may be formed ofmetal, ceramic, or other suitable materials. A plurality of pins may beformed on various locations of top surface 12. Corresponding to pins 170formed on surface 12, are receptacles 172. Receptacles 172 extend inwardfrom the surface of base section 125 that is to be joined to top surface12. Receptacles 172 preferably include a that 173 which is considerablygreater than the width of pins 170 such that, after optical housing 75is brought into contact with ceramic carrier 10 and pins 170 arereceived within corresponding receptacles 172, the components may bealigned in the x, y direction to maximize the optical couplingefficiency, before the components are permanently joined. An epoxy maybe introduced into receptacles 172. Next, the units are preferablyaligned with respect to one another, and the epoxy cured to secure thecomponents into position with respect to one another. According to theexemplary embodiment in which base section 125 surrounds the cavity orterraced cavity formed in ceramic carrier 10, the pin 170/receptacle 172feature may be included at various locations where base section 125contacts top surface 12. According to another exemplary embodiment, basesection 125 may consist of a plurality of legs and one or more of thelegs may include one or more receptacles 172 for receiving acorresponding pin 170 formed on surface 12.

FIG. 16 also shows a plurality of mounting pins 120 which extendorthogonally from bottom surface 8 of ceramic carrier 10. Mounting pins120 preferably extend along the direction generally parallel todirection 52 along which VCSEL 2 emits light. Mounting pins 120 will bediscussed further below.

FIG. 17 is a cross-sectional view of an exemplary ceramic carrier 10.Ceramic carrier 10 includes top surface 12 and recessed portion 180which includes recessed surface 181. Recessed portion 180 may preferablybe formed by including an appropriate cutout in the top ceramic layer orlayers prior to assembly. According to this exemplary embodiment, theglass member which covers and which may hermetically seal cavity 73 suchas glass cover 48 shown in FIGS. 10, 10A and 11, may be joined torecessed surface 181 within recessed portion 180. Similarly, baseportion 125 of optical housing 75 including ledge 160 such as shown inFIG. 16, may also be joined to recessed surface 181 of recessed portion180. Likewise, pins such as pins 170 shown in FIG. 16, may be formed toextend from recessed surface 181 according to various exemplaryembodiments.

FIG. 18 is a perspective view of an exemplary ceramic carrier 10including recessed portion 180, terraced cavity 6, angledreflective/transmissive member 44 disposed within terraced cavity 6, andexternal sidewalls 9. One of the external sidewalls, namely externalsidewall 9A, is configured to be mounted along a mounting surface (notshown). External sidewall 9A includes notches 184 which extend alongexternal sidewall 9A from top surface 12 to bottom surface 8. In theexemplary embodiment shown, notches 184 extend generally orthogonallywith respect to top surface 12 and bottom surface 8, and generallyparallel to the direction along which the VCSEL included within terracedcavity 6, emits light. In the exemplary embodiment shown, notches 184are semi-cylindrical in shape, but other configurations may be usedalternatively. Notches 184 may have conductive castellations formedtherein, the conductive castellations capable of being joined toconductive components formed on a mounting surface to which externalsurface 9A will be joined, such as by soldering. Notches 184 are alsocapable of coupling electrical components and conductive traces formedwithin the various layers of multilayer ceramic carrier 10. It will beshown that external sidewall 9A is mounted along the mounting surfacesuch that a VCSEL formed on base surface 17 (not shown) of terracedcavity 6 will preferably emit light in a direction generally parallel tothe mounting surface and therefore perpendicular to top surface 12,bottom surface 8, and base surface 17. Notches 184 include stop 186which produces discontinuous notches 184. In this manner, conductivematerial may extend only above or below stop 186, according to theillustrated embodiment, According to other exemplary embodiments, stop186 may not be used.

FIG. 19 is a plan view showing exemplary bottom surface 8 of exemplaryceramic carrier 10. Bottom surface 8 includes conductive traces 30 whichare electrically coupled by vias 32 to other components (not shown)within ceramic carrier 10. In an exemplary embodiment, conductive traces30 may be formed of metal such as gold or silver. The metal ispreferably chosen for maximum conductivity and also in conjunction withthe materials (e.g. HTCC or LTCC) and method used to form ceramiccarrier 10. According to the exemplary embodiment shown in FIG. 19,conductive traces 30 are formed adjacent edge 191 which forms part ofexternal sidewall 9A which is to be joined to a mounting surface, aswill be shown below. This arrangement minimizes the electrical path asignal must traverse when external sidewall 9A is joined to the mountingsurface along which the electrical signals travel. According to otherexemplary embodiments, in which ceramic carrier 10 is mounted usingother configurations, the conductive traces will be similarly clusteredaround the electrical connection point to minimize the distance and tominimize the routing of the electrical signal.

FIGS. 20, 21, 22 and 23 show various exemplary arrangements for mountingthe optical subassembly consisting of the ceramic carrier and opticalhousing, onto a printed circuit board or other daughter board ormounting surface. In each of the exemplary embodiments, one of theexternal sidewalls of the ceramic carrier is conterminously mounted onthe mounting surface. In each case, the pattern on the bottom surface ofthe ceramic carrier of the optical subassembly is preferably arranged sothat the conductive traces formed on the bottom surface are formedadjacent the external sidewall which is mounted on the mounting surface.This ensures high-quality electrical connection with constant impedancecharacteristics such as required in high-frequency applications. Thevarious exemplary embodiments shown and described provide for mountingthe OSA on a mounting surface such that the base of the terraced cavityis generally perpendicular to the mounting surface on transmitterembodiments. In TOSA embodiments, the emitting surface of the VCSEL ismounted normal to the mounting surface and adapted to transmit anoptical signal along an optical transmission medium configured parallelto the mounting surface. In receive embodiments, the absorbing surfaceof the vertically receiving photodetector is oriented normal to themounting surface and therefore adapted to receive an optical signalpropagated along a direction generally parallel to the mounting surface.In each case, the fiber launch direction is generally perpendicular tothe mounting surface, and the fiber and optical ferrule are received andsecured within an aperture formed in the optical housing and positionedgenerally parallel to the surface on which the OSA is mounted. Accordingto the exemplary embodiments, the mounting surface may be a printedcircuit board formed of suitable material, such as FR4, Duroid, Isociad,Arlon, or other suitable conventional materials. According to otherexemplary embodiments, the OSA may be mounted on a board other than theprinted circuit board materials described above.

FIG. 20 shows an exemplary method for mounting OSA 130 on a printedcircuit board or other daughter board by joining ceramic carrier 10 tothe mounting surface. In the exemplary embodiment, top surface 12 ofceramic carrier 10 is the surface of ceramic carrier 10 to which opticalhousing 75 is mounted and from which a cavity for retaining the opticalelement(s) extends. A VCSEL contained within ceramic carrier 10 emitslight generally orthogonal to top surface 12. As mounted on surface 202of printed circuit board 200, external sidewall 9A is conterminouslyjoined to mounting surface 202. In this manner, top surface 12 andbottom surface 8 of ceramic carrier 10 now appear respectively as theright and left-hand sides of the mounted ceramic carrier 10, as shown inFIG. 20. For consistency, top surface 12 and bottom surface 8 of ceramiccarrier 10 will continue to be referred to as “top surface 12” and“bottom surface 8” hereinafter.

In the exemplary embodiment shown in FIG. 20, J-Ieads 204 are used tomount optical subassembly 130 onto mounting surface 202. In an exemplaryembodiment, J-leads 204 may be formed of metal and are preferablysoldered or brazed to each of top surface 12 of ceramic carrier 10 andmounting surface 202 of printed circuit board 200. Conventionalsoldering methods may be used. Other methods may be used to join theJ-leads to the ceramic carrier and the mounting surface. In an exemplaryembodiment, J-Ieads to 204 may be brazed to pads 203 formed on each oftop surface 12 of ceramic carrier 10 and mounting surface 202. J-Ieadsmay be formed of rigid materials such as metals or ceramics. They may beformed of gold or gold-coated kovar in exemplary embodiments. TheJ-leads may be formed of other rigid materials in other exemplaryembodiments. According to another exemplary embodiment, J-Ieads 204 mayalternatively or additionally be used to join bottom surface 8 tomounting surface 202. According to one exemplary embodiment, J-leads 204are formed of conductive material and additionally carry electricalsignals between features of printed circuit board 200 and conductivetraces formed on ceramic carrier 10. In another exemplary embodiment,J-leads 204 may be used only for mechanical support. In the exemplaryembodiment shown in FIG. 20, an optical ferrule including an opticalfiber may be received within aperture 129 of barrel section 127 ofoptical housing 75. The VCSEL (not shown) contained within ceramiccarrier 10 emits light along direction 52, which is parallel to mountingsurface 202.

Referring to FIG. 21, another exemplary embodiment for mounting ceramiccarrier 10 onto mounting surface 202 of printed circuit board 200 isshown. For simplicity and clarity, the optical housing to which ceramiccarrier 10 is joined, is not shown in FIG. 20. In the exemplaryembodiment shown in FIG. 20, pins 210 may be joined to solder pads 212formed on either or both of top surface 12, as shown in FIG. 20, orbottom surface 8 (not shown). In an exemplary embodiment, pins 210 maybe formed of gold or gold coated kovar, but other materials may be usedalternatively. Conventional methods may be used to solder or braze pins210 onto solder pads 212. Corresponding holes 208 are formed in printedcircuit board 200 to receive pins 210. After pins 210 are fixed toceramic carrier 10 as above, ceramic carrier 10 is mounted onto printedcircuit board 200 by inserting pins 210 into corresponding holes 208formed in printed circuit board 200. After pins 210 are inserted intocorresponding holes 208, conventional soldering techniques arepreferably used to secure the ceramic carrier 10 into place. In analternative embodiment (not shown), pins may be affixed to each of topsurface 12 and bottom surface 8 of ceramic carrier 10 and inserted intocorresponding holes formed on printed circuit board 200. This providesadded stability. According to one exemplary embodiment, pins 210 maycarry a signal between components of printed circuit board 200 andcomponents of ceramic carrier 10, and according to another exemplaryembodiment, pins 210 may be used only for mechanical stability purposes.

FIG. 22 is a side view showing ceramic carrier 10, including mountingpins 216 which extend orthogonally from bottom surface 8. Mounting pins216 extend along external sidewall 9A, which is mounted on surface 202of printed circuit board 200. Pins 216 may be formed of metal, Kovar, orother suitable materials. The base of mounting pins 216 may be formed ofKovar or Alloy 42, but other materials may be used alternatively.Mounting pins 216 may preferably be plated with a layer of nickel orgold over the base portion. Pins 216 may provide mechanical support andmay be soldered or epoxied onto surface 202. Pins 216 may also conductan electrical signal according to various exemplary embodiments.According to such an exemplary embodiment, pins 216 may be electricallycoupled to conductive traces 218 formed on surface 202 by means ofsolder bond 220. Conventional soldering techniques may be used.According to this exemplary embodiment, pins 216 may extend along andcontact surface 202.

The J-leads and distinctive pins shown in FIGS. 20-22 are intended to beexemplary only. Other exemplary pin configurations may be used to jointhe ceramic carrier to mounting surface 202, such that the verticallyemitting or receiving optoelectronic device within ceramic carrier 10,configured to receive or emit light along a direction parallel tomounting surface 202.

FIG. 23 shows an expanded portion of ceramic carrier 10 joined tomounting surface 202 of printed circuit board 200. Conductive trace 30extends between layers of the multilayer ceramic carrier 10 and is wirebonded to VCSEL 2 by means of wire bond 18. VCSEL 2 emits a light alongdirection 52, which is parallel to surface 202. Ceramic carrier 10includes a plurality of notches 184 indicated by the dashed lines.Ceramic carrier 10 is joined to surface 202, such that the castellationsformed within notches 184 are contacted to conductive trace 218 bysoldering or other means. Conductive trace 218 is formed on surface 202.In this manner, the electrical signal path is preferably minimized andinductance is controlled. An electrical signal propagating fromconductive trace 218 to VCSEL 2 desirably travels along the shortestelectrical path. In order to preferably minimize the impedance mismatchof the electrical signal and to minimize loss due to signal reflection,microwave stub portion 219 of conductive trace 218 may be eliminatedsuch that distance L of microwave stub 219 is zero. According to anotherexemplary embodiment, microwave stub 219 may be retained to tune theimpedance. To ensure that microwave stub 219 is avoided, a stop, such asstop 186 shown in FIG. 18, may be used to ensure that the electricalsignal path does not extend past the point where conductive trace 218intersects conductive trace 30.

It should be emphasized that each of the embodiments shown and discussedin FIGS. 20-23 apply equally to mounting a receive optical subassemblyincluding a vertically receiving optical element such as a conventionalphotodetector, onto a mounting surface to receive light propagated alongan optical fiber held parallel to the mounting surface.

FIG. 24 is a front view showing ceramic carrier 10 mounted on mountingsurface 202 of printed circuit board 200. Ceramic carrier 10 includesterraced cavity 6 and base surface 17, preferably perpendicular tomounting surface 202. Ceramic carrier 10 includes notches 184 formedalong external sidewall 9A, which is mounted on mounting surface 202.Notches 184 are semi-circular in the exemplary embodiment shown and maybe filled with conductive material to form castellations and conductelectrical signals, such as shown in FIG. 23.

FIG. 25 is a perspective view showing another exemplary embodiment andanother aspect of the present invention. FIG. 25 shows opticalsubassembly 130, including optical housing 75. Optical housing 75includes base section 125, which includes four legs 134. In thisembodiment, once optical housing 75 is joined to top surface 12 ofceramic carrier 10, an open space 132 exists between portions of opticalhousing 75 and ceramic carrier 10, even with cover glass 48 in positionon top surface 12.

FIG. 25 also shows a row of mounting pins 120, that extend orthogonallyfrom bottom surface 8 of ceramic carrier 10 and enable OSA 130 to bemounted adjacent an edge of a printed circuit board or other mountingboard. As such, mounting pins 120 are generally parallel to the fiberlaunch direction and the direction along which a VCSEL formed withinceramic carrier 10 emits light. Mounting pins 120 are orthogonal to theemitting surface of a VCSEL or orthogonal to the receiving surface of avertically receiving device, according to the embodiment in which OSA130 is a ROSA. Although mounting pins 120 extend substantiallyperpendicularly from bottom surface 8 in the exemplary embodiment shown,other arrangements may be used alternatively. In the exemplaryembodiment shown, the linear array of mounting pins 120 is disposedgenerally centrally within bottom surface 8. The exemplary row ofmounting pins 120 may be formed to extend from bottom surface 8 at anyof various locations.

Mounting pins 120 may be electrically conductive in an exemplaryembodiment and may be electrically coupled to the optical element andother optoelectronic components contained within ceramic carrier 10.Bottom surface 8 may include conductive traces formed thereon and whichextend to conductive mounting pins 120. According to the embodiment inwhich mounting pins 120 are conductive, the base of conductive mountingpins 120 may be formed of Kovar or Alloy 42, but other materials may beused alternatively. The conductive pins may each be plated with a layerof nickel and a layer of gold over the base portion. It will be seenthat the linear array of mounting pins 120 will be joined to the surfaceof a printed circuit board, along the edge of the printed circuit board.Mounting pins 120 are joined to a surface of a printed circuit boardsuch that optical subassembly 130 is mounted adjacent the edge of theprinted circuit board, such that portions of optical subassembly 130extend above the printed circuit board surface and portions of opticalsubassembly 130 extend below the surface of the printed circuit board.Since optical subassembly 130 is not mounted directly over the printedcircuit board and at the expense of vertical module space, it can be ofincreased size and can advantageously include additional componentswithin ceramic carrier 10. The VCSEL or vertically receiving opticaldevice is preferably oriented to emit or receive light which travelsalong a fiber launch direction which is parallel to the printed circuitboard. According to the embodiment in which mounting pins 120 areconductive, they may advantageously be coupled to correspondingconductive pads which are formed along the edge of the printed circuitboard and which are electrically coupled to conductive traces anddevices formed on the printed circuit board.

Other arrangements of mounting pins 120 may be used alternatively.According to one exemplary embodiment, mounting pins 120 may be formedin a linear array but spaced irregularly. According to another exemplaryembodiment, two parallel rows of mounting pins 120 may be used.According to this exemplary embodiment, the pair of rows of mountingpins formed on the OSA 130 may be joined to each of respective top andbottom surfaces of the printed circuit board.

FIG. 26 is another perspective view of optical subassembly 130, whichincludes a linear array of mounting pins 120. According to yet anotherexemplary embodiment, the mounting pins 120 may be non-conductive.According to one exemplary embodiment, non-conductive pins may beinterposed between conductive pins along a common row, such as depictedin FIGS. 25 and 26. Mounting pins 120 formed of conductive ornon-conductive material are preferably used to mechanically couple OSA130 and a printed circuit board.

In the exemplary embodiment in which mounting pins 120 are conductive,bottom surface 8 of ceramic carrier 10 may include a metal or conductivepattern formed thereon. The conductive material on ceramic carrier 10may preferably be soldered to the printed circuit board at a 90° angleto effectuate the electrical connection. The dimensions and spacing ofthe patterned conductive material on the ceramic carrier are preferablylimited only by the printing technique and not the electrical couplingtechnique. In this manner, a high density of electrical connection maybe achieved.

FIG. 27 is a side view of OSA 130, including optical housing 75 andceramic carrier 10. A linear array of mounting pins 120 extendsorthogonally from bottom surface 8. In the exemplary embodiment shown,mounting pins 120 may include length 122 of two millimeters, but otherlengths may be used alternatively. According to an exemplary embodiment,mounting pins 120 may be arranged in a linear array of nine mountingpins 120 and may include a pitch 124 of 1.27 millimeters or 50 mils,according to exemplary embodiments, but various other pitches may beused alternatively. According to one exemplary embodiment, opticalhousing 75 may be formed of plastic and may include height 142, whichmay be on the order of 12.86 millimeters according to one exemplaryembodiment, but various other heights 142 may be used according tovarious other exemplary embodiments.

An advantage of exemplary OSA 130 of the present invention, whichincludes mounting pins 120 and is therefore edge-mounted adjacent anedge of a printed circuit board, is that the entire OSA need not bepositioned over the printed circuit board. In this manner, there areless space constraints and design restrictions, and the lateraldimensions of ceramic carrier 10 (the length and width of each of topsurface 12 and bottom surface 8) may be relatively large, and the cavityor terraced cavity formed extending inwardly from top surface 12, may becorrespondingly large enough to include additional semiconductor andelectronic components besides the primary optoelectronic device.Additional components which may be included in the ceramic package ofthe OSA are resistors, monitor diodes and other photodetectors,capacitors, inductors, and laser diode drivers in the exemplaryembodiment in which the OSA is a transmit optical subassembly. Accordingto the exemplary embodiment in which the optical subassembly is a ROSA,transimpedance amplifiers, transimpedance limiting amplifiers,resistors, capacitors, inductors, and high-speed detectors may be amongthe components additionally included within the OSA. As above,edge-mounted OSA 130 may extend both above and below the printed circuitboard or, according to another exemplary embodiment, mounting pins 120may be arranged such that edge-mounted OSA 130 extends essentially onlyabove, or essentially only below, the printed circuit board.

According to an exemplary embodiment, the lateral dimensions of each ofopposed top surface 12 and bottom surface 8 may be at least 13×8millimeters, and in an exemplary embodiment may be 13×8.5 millimeters.Other dimensions may be used alternatively. The distance between opposedsurfaces 12 and 8, i.e., the height of ceramic carrier 10, may vary, andin an exemplary embodiment, may be 1.73 millimeters. Such dimensions areintended to be exemplary only and will vary depending on variousapplications and space concerns.

Still referring to FIG. 27, the method for joining optical carrier 75 toceramic carrier 10, more particularly the alignment tolerance in joiningthe components, is advantageously improved because of the increased sizeof ceramic carrier 10, possible due to the fact that the opticalsubassembly is not mounted completely over the printed circuit board orother mounting surface. According to the method for joining thecomponents, epoxy 136 is preferably introduced to the interface formedbetween legs 134 of optical housing 75 and top surface 12 of ceramiccarrier 10. Various suitable UV-curable epoxies, visible light-curableepoxies, or RF-curable epoxies may be used. Legs 134 of optical housing75 are brought into contact with top surface 12, such that opticalhousing 75 generally straddles glass cover 48. Optical housing 75 isaligned such that cylindrical portion 127 is generally positioned overcavity 73 which may be a terraced cavity, and centered over VCSEL 2,formed in cavity 73, according to an exemplary embodiment. FIG. 27 is aside view of the arrangement, and that each side of optical housing 75includes multiple legs 134. That is, each of the two illustrated legs134 represents a set of legs extending perpendicularly to the plane ofthe figure. Before optical housing 75 is permanently joined to ceramiccarrier 10, the optical elements in ceramic carrier 10 and opticalhousing 4 will preferably be aligned to one another.

The alignment process may involve aligning a VCSEL or a verticallyreceiving optical element to an optical fiber secured within cylindricalportion 127 of optical housing 75. During the alignment process, thecomponents may be moved freely relative to one another along thedirection perpendicular to the plane of the page. Along the x-direction,as shown in FIG. 27, legs 134 of optical housing 75 and glass cover 48are sized such that a total spacing of 500 microns may be achievedbetween the inside of legs 134 and outer edges 138, 140 of glass cover48. This preferably provides an alignment tolerance in the x-directionas well as the y-direction. After acceptable assignment is achieved, UVradiation, or visible light is used to cure epoxy 136 and fix opticalhousing 75 in position with respect to ceramic carrier 10. The joinedunits include open space 132 between the components. The alignedcomponents will include the optical fiber contained in cylindricalportion 127, being aligned with VCSEL 2 or the vertically receivingoptical element disposed in cavity 73. Cylindrical portion 127 andoptical housing 75 may essentially be centered with respect to ceramiccarrier 10, or they may be off center according to various exemplaryembodiments. After the units are fixed into position with respect to oneanother, a permanent epoxy, for example, a thermally-curable epoxy, ispreferably used to permanently join the components together. Varioussuitable thermally curable epoxies may be used. According to anotherexemplary embodiment, various other permanent epoxies, such asUV-curable epoxies, RF curable epoxies, and visible light-curableepoxies may be used. The permanent epoxy such as permanent epoxy 154shown in FIG. 28 may seal open space 132. Optical subassembly 130,including mounting pins 120 which extend from bottom surface 8, is nowready to be mechanically coupled to a printed circuit board.

FIG. 28 is a perspective view showing optical subassembly 130 coupled toedge 304 of printed circuit board 300. Optical subassembly 130 ismounted to printed circuit board 300, such that light emitted by a VCSELincluded within ceramic carrier 10 of optical subassembly 130 is emittedalong direction 52, parallel to the direction of optical fiber 312 andsubstantially parallel to surface 302 of printed circuit board 300 andthe circuitry formed thereon. According to either the TOSA or ROSAembodiment, the vertically emitting or vertically receiving opticalelement preferably includes an emitting or receiving surface mountedparallel to bottom surface 8 and normal to surface 302. Printed circuitboard 300 may be a conventional printed circuit board formed of suitablematerials, such as described above. Permanent epoxy 154 joins thecomponents of OSA 130.

Printed circuit board 300 preferably includes top surface 302 and edge304 to which OSA 130 is joined. Cover 310 may be a jacket, shrink tubingor other means used to secure optical fiber 312 to OSA 130. Opticalfiber 312 includes an optical fiber within an optical ferrule, which issecured within an aperture of optical housing 75. OSA 130 includes a rowof mounting pins 120, which are conductive in the exemplary embodimentand are joined to corresponding conductive pads 306, which are formed ontop surface 302 of printed circuit board 300 and extend inwardly fromedge 304. In the exemplary embodiment shown in FIG. 28, conductive pads306 are substantially orthogonal to edge 304 but may be orienteddifferently. Conductive pads 306 are electrically coupled to conductivetraces and other optoelectronic elements on printed circuit board 300.Conductive mounting pins 120 of optical subassembly optoelectronic 130are joined to corresponding leads 306 of printed circuit board 300, bysoldering in an exemplary embodiment. Other methods for electricallycoupling conductive mounting pins 120 to corresponding leads 306 may beused alternatively. OSA 130 is mounted to printed circuit board 300,such that it is disposed adjacent edge 304 of printed circuit board 300.It should be pointed out that, as mounted, optical subassembly 130includes portions which extend both above and below printed circuitboard 300 in the exemplary embodiment shown in FIG. 28.

FIG. 29 is a plan view showing exemplary printed circuit board 300.Printed circuit board 300 includes conductive pads 306 which terminateat edge 304 and are electrically connected to electrical circuitry onprinted circuit board 300 (not shown). Conductive pads 306 are formed tocorrespond to conductive mounting pins formed on an OSA, such asconductive mounting pins 120 shown in FIG. 28. In the exemplaryembodiment shown, printed circuit board 300 includes notch 320 extendinginwardly from edge 304. According to other exemplary embodiments, notch320 may not be used. According to one exemplary embodiment, a separateoptical subassembly may be joined to each of portion 322 and portion 324on opposed sides of notch 320 of printed circuit board 300. For example,a ROSA may be coupled to portion 322, and a TOSA may be coupled toportion 324, or vice versa. This is achievable, as a septum or metalshield may be received within notch 320 to electronically shield theTOSA from the ROSA and to prevent cross-talk between the components.According to an exemplary embodiment, the septum may be a part of theenclosure in which printed circuit board 300 is installed.

According to another aspect of the present invention, the ceramiccarrier of the optical subassembly may be mounted onto a mountingsurface such as the surface of a printed circuit board, using asolderless mounting technique. This technique may include various relieffeatures formed on or attached to the printed circuit or other board, tobe received in corresponding openings formed in the ceramic carrier.

Referring to FIG. 30, bracket 340 may be securely coupled to a printedcircuit board or other mounting surface, using conventional means suchthat legs 342 extend orthogonally from the printed circuit board.According to an exemplary embodiment, the bracket, including pins 342,may be formed of metal, but other rigid and mechanically stablematerials may be used in other embodiments. FIG. 30 also shows exemplaryceramic carrier 10 which includes holes 344. According to the exemplaryembodiment shown, two brackets 340 may be secured on a surface so as tosecure ceramic carrier 10 into position. It should be understood thatother bracket arrangements may be used alternatively. Holes 344 may beproduced by punching appropriate holes through the various layers ofceramic tape before they are joined together to form the multi-layerceramic carrier, or they may be formed by tooling after ceramic carrier10 has been formed. Other methods for forming holes 344 may be usedalternatively. Holes 344 are shaped and configured to receive acorresponding pin 342 of bracket 340. It can be seen that exemplaryholes 344 are tapered. In this manner, holes 344 accommodate generallyorthogonal pins 342 to be slid into holes 344 at the wider portion ofholes 344. Then, as ceramic carrier 10 is slid into place over bracket340, pins 342 become tightly nested within holes 344.

It should be understood that the bracket 340/holes 344 embodiment shownin FIG. 30 is intended to be exemplary only. Other protruding relieffeatures and corresponding openings for receiving the relief featuresmay be used according to other exemplary embodiments. For example, pinswhich are generally round, elliptical or other shapes in cross-sectionmay be used. According to another exemplary embodiment, after theprotruding relief features are introduced in corresponding openings inwhich they are nested, additional techniques may be used to secure therelief features into position. For example, conventional brazing orsoldering techniques may be used, or epoxy may be used to secure thecomponents.

According to yet another exemplary embodiment of the present invention,the optical housing may not be a unitary optical housing such as shownin FIG. 13, but, rather, it may be formed of multiple components joinedto enhance CTE (coefficient of thermal expansion) matching. FIG. 31 is across-sectional view of exemplary OSA 430 which includes ferrulereceptacle 475 joined to multilayer ceramic carrier 10 by means ofbridge 425. Multilayer ceramic carrier 10 is as described above.

Bridge 425 and ferrule receptacle 475 are separately formed, preferablyof different materials, to enhance CTE matching. In an exemplaryembodiment, ferrule receptacle 475 includes an integrally formed lens450 and is formed of plastic. Plastics such as Ultem 1010, Ultem 1000,Topas 5013 or Topas 5713 may be used, but other conventional plasticmaterials may be used according to other exemplary embodiments. Bridge425 is preferably formed of suitable metallic materials, but othermaterials may be used in alternative embodiments. Ferrule receptacle 475is bonded to bridge 425, which is bonded to ceramic carrier 10 which maybe an HTCC ceramic carrier in an exemplary embodiment. In an exemplaryembodiment, bonding materials such as epoxies may be used, but otherconventional bonding materials may be used alternatively.

Aperture 429 extends axially through ferrule receptacle 475 andessentially forms a hollow core of the cylindrical member. Aperture 429formed within ferrule receptacle 475, is configured to receive anoptical ferrule including an optical fiber or other optical transmissionmedium. OSA 430 shown in FIG. 31 may be a TOSA or ROSA. According toeither exemplary embodiment, light propagated along an opticaltransmission medium retained axially within aperture 429 of ferrulereceptacle 475 is received by or emitted from an optical componentdisposed within multilayer ceramic carrier 10. The arrangement shown inFIG. 31, is exemplary only, and various other configurations of ferrulereceptacle 475 and bridge 425, may be used alternatively.

The preceding merely illustrates the principles of the invention. Itwill thus be appreciated that those skilled in the art will be able todevise various arrangements which, although not explicitly described orshown herein, embody the principles of the invention and are includedwithin its scope and spirit. Furthermore, the examples described hereinare intended to aid the reader in understanding principles of theinvention and the concepts contributed by the inventors to furtheringthe art, and are to be construed as being without limitation to suchspecifically recited examples and conditions. Moreover, all statementsherein reciting principles, aspects, and embodiments of the invention,as well as specific examples thereof, are intended to encompass bothstructural and functional equivalents thereof. Additionally, it isintended that such equivalents include both currently known equivalentsand equivalents developed in the future; i.e., any elements developedthat perform the same function, regardless of structure. The scope ofthe present invention, therefore, is not intended to be limited to theexemplary embodiments shown and described herein. Rather, the scope andspirit of the present invention is embodied by the appended claims.

1-43. (canceled)
 44. An optical element comprising a carrier containingan optical source therein and adapted to be joined to an opticalhousing, said carrier including a top surface and an opposed bottomsurface being generally parallel to said top surface, a terraced cavityextending down from said top surface and including interior sidewallsand a base surface, said terraced cavity including: terraces formed atdifferent heights on opposed interior sidewalls; said optical sourcedisposed on said base surface, capable of emitting light along adirection generally orthogonal to said top surface, and wire bonded to aconductive trace formed along a terrace of said terraced cavity; and aphotodetector disposed therein and being capable of detecting lightemitted by said optical source.
 45. The optical element as in claim 44,wherein said carrier is formed of one of a dielectric material and apolymeric material.
 46. The optical element as in claim 44, wherein saidcarrier is formed of ceramic.
 47. The optical element as in claim 44,wherein said optical source comprises a VCSEL.
 48. A multilayer ceramiccarrier formed of a plurality of stacked ceramic layers and including aphotodetector therein, said multilayer ceramic carrier including abottom surface and an opposed top surface being generally parallel tosaid bottom surface, a terraced cavity extending down from said topsurface and including interior sidewalls and a base surface, saidphotodetector disposed on said base surface and oriented to detect lightdirected into said terraced cavity and generally perpendicular to saidbase surface, said terraced cavity including at least one terrace formedon at least one of said interior sidewalls, at least one of saidplurality of ceramic layers including conductive traces thereon, suchthat said multilayer ceramic carrier therefore includes conductivetraces interposed between at least a pair of adjacent stacked ceramiclayers, at least a part of one of said conductive traces extending alonga terrace of said terraced cavity and terminating within said terracedcavity.
 49. The multilayer ceramic carrier as in claim 48, wherein saidphotodetector is wire bonded to said part of one of said conductivetraces which extends along said terrace of said terraced cavity andterminates within said terraced cavity.
 50. The multilayer ceramiccarrier as in claim 48, further comprising a further electronic devicedisposed within said terraced cavity, said further electronic devicebeing electrically coupled to said photodetector and wire bonded to atleast one of said conductive traces.
 51. The multilayer ceramic carrieras in claim 50, wherein said further electronic device comprises one ofa transimpedance amplifier and a limiting amplifier integrated circuit.52. The multilayer ceramic carrier as in claim 48, in which saidphotodetector includes an absorbing surface and further comprising anoptical housing attached to said ceramic carrier, said optical housingretaining an optical fiber therein, said optical fiber orientedgenerally perpendicularly to said absorbing surface.
 53. The multilayerceramic carrier as in claim 48, wherein said photodetector comprises ap-i-n photodiode. 54-135. (canceled)